Dyntopo creating spikes or stretched sculpt result on mesh
I made a quick test and it might be also that your object has other scale than 1,1,1.

The solution is to have your object selected and in the object mode press Ctrl+A and select Scale from the Apply menu.

Here I have more than 15 for the Z scale of a cube and the dyntopo sculpt result with the same settings as yours is quite stretched, like yours.



After applying the scale to 1,1,1, dyntopo behaves way nicer, again with the same dyntopo settings as yours: